George Carlin had a great quote regarding child safety but this is a family forum.
I think there is a height and/or weight requirement to go into and eventually without a booster. Never heard of a front seat rule on age. After all as mentioned a single cab has no option but does have airbag override.
Speski OffRoad LTD, Cargo Solutions for Toyota 4x4's http://www.SpeskiOffRoad.com
"80 series, with a fridge"
1976 FJ40, Project with little progress.
2004 Starcraft 10RT